Steel for saw blades

ABSTRACT

A sawblade consisting essentially of 0.6-0.9% C, 0.5-1.0% Si, 0.4-1.0% Mn, 0.4-1.0% Cr, 0.2-0.8% Mo, 0.3-1.0% Ni, at least one element in an amount of up to 0.3% selected from the group consisting of Ti or V, remainder iron and residual impurities; the microstructure of the sawblade being bainitic which has been hardened to a hardness range of 46-54 HRc.

United States Patent Kulmburg [451 May 16, 1972 STEEL FOR SAW BLADESReferences Cited [72] Inventor: Alfred Kulmburg, Kapfenberg, AustriaUNITED STATES PATENTS 73 Assignee; m; Bohler & Cm Akfi e eu haft1,464,174 8/1923 Finkl 148/36 K f b Austria 1,660,790 2/1928 Herman75/128 w 2,289,081 7/1942 Shortell et 21.... ..29/95 I Ffledi 19703,131,056 4/1964 0111161116161... 75/128 w 3,507,633 4/1970 Dewez..29/183 1. N [2]] App 102 913 3,528,088 9/1970 Seghe711et a] ..148/36 x[30] Foreign Application Priority Data Primary Examiner-Charles N.Lovell Jan. 9, 1970 Austria ..Al62/70 Stem [57] ABSTRACT 52] 11.8. C1..148/36, 29/95, 30/166,

75 23 w 143 133 A sawblade consisting essentially of 0.60.9% C, 0.51.0%Si, 51 Int. Cl. ..C2ld 9 24, C22C 39/20, 823p 15/28 04-19% Mn, Cr,02-03% 1 03-10% Ni, 4! [58] Field 61 Search ..75 128 v, 128 w; 148/36;least one element In an amount of p to 033% Selected from the groupconsisting of Ti or V, remainder iron and residual impurities; themicrostructure of the sawblade being bainitic which has been hardened toa hardness range of 46-54 l-lR 3 Claims, N0 Drawings STEEL FOR SAWBLADES The invention relates to saw blades having bainticmicrostructure.

Generally in the fabrication of blades for power-saws, chain-saws,resaws, wide-band saws and wood/timber-saws, steels are used whichpossess on one hand a very hard surface and on the other a relativelytough core. To satisfy the requirements for this purpose, the Germanstandard steel designations C 70 W1, C 87 WS and C 85 WS according ASl-Wl) are suggested for the fabrication of such sawblades. For more severeservice conditions the sawblades are fabricated of 80 Cr, V 2.

All these steels are used in quenched and tempered conditions. lnservice saws blades must be wear-resistant as well as tough. Thesecontrary properties are practically unobtainable in one tool. l-lighwear resistance which means a high hardness usually means a such greatloss in toughness which causes the sawblades to be replaced because thesingle chain-links of sawblades fracture. If one lowers thewear-resistance to obtain a higher toughness, then the service-life ofthe sawblades is very much reduced by early wear.

Extensive experiments have shown, that it is possible to usemachine-saw-steels for sawblades having bainitic instead of martensiticmicrostructure in tempered condition. it was discovered, that steelswith 0.6-0.9% C, 05-10% Si, 0.4-l.0% Mn, 0.4-l.0% Cr, 02-08% Mo, O.3l.0%Ni, possibly up to 0.3% Ti and/or V, remainder iron and residualimpurities, possess when in bainitic hardened condition with a hardnessof 46-54 Hr an optimal toughness.

For example, a steel with 0.68-0.73% C, O.80-1.00% Si, 0.35-0.50% Mn,OAS-0.60% Cr, 0.250.35% Mo, 0.55-0.75% Ni, remainder iron, wasaustenitised between 860880 C, followed by a treatment in a molten bathbetween 2903 30 C. After an isothermal holding time of approximately60-90 minutes the cooling took place in still air. After this heattreatment the steel was in a bainitic condition.

The hardness of this steel was 51-52 HR.

The notch impact strength measured on five test pieces, was between 29and 31 mkp/cm. For comparison, test pieces of the same steel were heattreated by the conventional method of quenching followed by temperingand were found to possess a hardness of 51-52 l-lRc as well. The notchimpact strength of these samples however was only at the 2.5-3.5 mkp/cmThe instant invention is therefor the use of particular steels having06-09%C, 0.5-1.0% Si, 0.41.0% Mn, 0.4-1.0% Cr, 0.2-0.8 Mo, O.3l.0% Ni,possibly up to 0,3 Ti and/or V, remainder iron and residual impurities,in bainitic hardened condition with a hardness of 46-54 l-lRc for themanufacture of chain saws.

This steel is also very suitable for long-band-saws, which areparticularly stressed by buckling at the sides.

Although the invention has been described in detail, it is to beunderstood that this does not delimit the invention. The spirit andscope of this invention is limited only by the language of the appendedclaims.

What we claim is:

1. A sawblade consisting essentially of 0.6-0.9% C, 0.5-1.0% Si,0.4-1.0% Mn, O.4l.0% Cr, 0.20.8% Mo, 0.3-1 .0% Ni, at least one elementin an amount of up to 0.3% selected from the group consisting of Ti orV, remainder iron and residual impurities; the microstructure of thesawblade being bainitic which has been hardened to a hardness range of46-54 HR.

2. The sawblade as claimed in claim 1 wherein the composition is0.68-0.73% C, 0.80-1.00% Si, 0.35-0.50% Mn,.

0.550.75% Ni, the

2. The sawblade as claimed in claim 1 wherein the composition is0.68-0.73% C, 0.80-1.00% Si, 0.35-0.50% Mn, 0.45-0.60% Cr, 0.25-0.35%Mo, 0.55-0.75% Ni, the remainder iron and residual impurities.
 3. Thesawblade as claimed in claim 1 which has a notch impact strength ofbetween 29 and 31 mkp/cm2.